Electronic devices containing active organic materials are attracting increasing attention for use in devices such as organic light emitting diodes (OLEDs), organic photoresponsive devices (in particular organic photovoltaic devices and organic photosensors), organic transistors and memory array devices. Devices containing active organic materials offer benefits such as low weight, low power consumption and flexibility. Moreover, use of soluble organic materials allows use of solution processing in device manufacture, for example inkjet printing or spin-coating.
An OLED may comprise a substrate carrying an anode, a cathode and one or more organic light-emitting layers between the anode and cathode.
Holes are injected into the device through the anode and electrons are injected through the cathode during operation of the device. Holes in the highest occupied molecular orbital (HOMO) and electrons in the lowest unoccupied molecular orbital (LUMO) of a light-emitting material combine to form an exciton that releases its energy as light.
Suitable light-emitting materials include small molecule, polymeric and dendrimeric materials. Exemplary light-emitting polymers include poly(arylene vinylenes) such as poly(p-phenylene vinylenes) and polyarylenes such as polyfluorenes.
WO 2005/049546 discloses polymers having a repeat unit of formula:
wherein Ar is a substituted or unsubstituted aryl group, Ar″ is a substituted or unsubstituted arylene group and Z is a polycyclic arylene. In one example, Z is fluorene.
US 2011/0175072 discloses an OLED including an emitting layer doped with an iridium complex and with a compound of formula:
wherein Ar is aryl and X is an arylene group, for example phenylene, biphenylene and spirofluorenylene.
KR 2011/057078 discloses a compound having the following formula:
wherein Ar is biphenyl, fluorenyl or tetrahydropyrenyl, R1, R2 and R3 are H or certain substituents, Het1 and Het2 are substituted or unsubstituted C3-20 heteroaryl, and n is 0-20.
US 2004/109955 discloses repeat units having the following formula:

Wherein Ar1, Ar2, Ar3 and Ar4 each independently represent an arylene group or divalent heterocyclic group; E1, E2 and E3 each independently represent an aryl group which has three or more substituents selected from certain substituents or a heterocyclic group which has one or more substituents selected from certain substituents, a and be each independently represent 0 or 1 and 0≤a+b≤1.